Recently, in proportion to the rapid development of computer networks, information is provided through networks, and many users acquire information from networks. Furthermore, the quantity of information provided through networks increases, and a frequency to update the information becomes high (For example, several times every day). Accordingly, it is important how to effectively retrieve and collect information including Internet information. Furthermore, similar status exists in LAN inside company. If LAN inside home widely spreads, similar status also exists.
As one information retrieval method, a remote retrieval is often utilized. In the remote retrieval, a retrieval message is sent to a host computer storing the information whenever one retrieval request is input, and the retrieved information is received. However, if a plurality of retrieval requests is continuously input, sending/receiving of the retrieval messages creates a bottleneck.
As another retrieval method, a mobile agent retrieval, which can realize smooth retrieval, is utilized. In the mobile agent retrieval, a retrieval program storing a retrieval request is sent to a retrieval destination host, and the retrieval is locally executed in the retrieval destination host. Even if a large number of retrieval requests are input, sending and receiving times of the retrieval message are short. However, the retrieval program storing the retrieval result moves from one retrieval destination host to another retrieval destination host. Accordingly, in case that moving times are long, the communication cost becomes high.
On the other hand, by mirroring technique of a Web server or a database, a copy of the desired information often exists in a network in addition to a master of the desired information. Furthermore, in view of information contents or retrieval purpose, it does not matter that a copy of the desired information is obtained instead of the original. However, in a plurality of selection items including one master and at least one copy, it is unknown how to select an item to be accessed and how to access the selected item. No guidance to effectuate the information retrieval is given for the information collection system.